Irlen (see appendix) has discovered empirically that a small percentage of the population can read better using colored lenses. Her findings were confirmed by Adler and Atwood (see appendix) who showed that Irlen lenses improved length of sustained reading and decreased headaches. Possible explanations for this include a lack of visual yellow, a pigment found in the fovea which absorbs blue light. Blue light does not affect fine visual resolution and may create destructive chromatic aberration. Also, color vision depends on the comparison of outputs of cones. Another explanation is that the output of the cones may be misconnected as Galaburda (see appendix) has shown anatomic differences in the brains of dyslexics.